Film-Tech Forum ARCHIVE: SH-1000 flutter woes

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Posted by Scott Norwood (Member # 30) on 02-04-2007, 07:07 AM:

What would cause flutter issues on an SH-1000 with a Century C on top of it? Dialogue isn't so bad, but music is very nearly unlistenable. The flutter doesn't seem to change from the beginning of a (2000') reel to the end of it.

Some history: the theatre had this problem a couple of years ago and it was supposedly "fixed" by replacing a gear in the projector head (I don't know which one, nor do I completely trust the individual who replaced it). For a variety of reasons not relevant here, I recently diassembled this projector (removed Century head, removed soundhead flywheel, removed motor, removed soundhead from base) and reassembled it. The flutter problem is back.

This suggests to me that there is something critical about the alignment of either the projector head or the motor, but I haven't been able to get rid of the flutter issue by making adjustments to either. Another possibility is that the previous "fix" wasn't done correctly and that the issue was never really fixed properly.

Has anyone had this issue before and, if so, what else should be checked/adjusted? Thanks.

Posted by Louis Bornwasser (Member # 3063) on 02-04-2007, 07:59 AM:

Flat spots on impedance roller?

Bad bearings in impedance roller or sound drum? Can't be much else unless impedance flanges are very very worn. Louis

Posted by Gordon McLeod (Member # 33) on 02-04-2007, 09:05 AM:

The other possibility is the flywheel
I have seen them dropped or leak and the inner floating flywheel starts to touch or bind against the outer shell
In the old WE books they reffered to this as whiskers

Posted by Dave Macaulay (Member # 813) on 02-04-2007, 10:52 AM:

Since there's a slack loop between the projector and soundhead, the projector won't directly produce any flutter in the sound.
What speed is the flutter, and is it constant? A Dolby tone loop will give a fairly constant tone to listen to, just don't interpret the built-in warbles as flutter.
First thing to check is the lay-on roller, and then the impedance drum bearings. The lay-on roller usually causes a flutter or warble every turn. Bad bearings are easy to feel if you remove the "flywheel". You can test the impedance "flywheel" by turning it at about normal speed then suddenly stopping it, holding it still a moment, then releasing it. It should start turning again, not as fast as before.
The top sprocket in the soundhead pulls film through the impedance drum and if the sprocket rotation speed isn't constant it will cause flutter, you may be able to feel it with a finger touching the film betwen the drum and sprocket.
Projector drive problems: the driving gears being meshed too tightly can cause speed variations. The drive gear should be set "tight" and then loosened off enough to be free turning. There may be an eccentric screw in the projector mounting to adjust this, usually it's gone.
The motor may be misaligned enough to cause a speed variation but I doubt it, usually it just causes a lot of vibration in the whole unit. A bad flex coupling might be at fault too, but that would cause a flutter at motor shaft speed as far as I can imagine. If that's what you have, check the motor mount alignment.
End force on the gearbox shaft may be a problem too, the "motor" shaft should be driven against the motor end bearing by a spring in the opposite end. If you're pushing in on the shaft with the motor mount, the shaft may be floating axially and could rock back and forth with any load variations. That would give you some flutter.
Since apparently it was OK before you worked on it, I would check all the alignment issues with the soundhead/projector and soundhead/motor very carefully.

Posted by Mark Gulbrandsen (Member # 72) on 02-04-2007, 11:53 AM:

Also check the SN171 upper lateral guide roller bracket to be sure it is not cracked. The cracking of this bracket is actually more common today than bad gears in the gear box. Crappy Simplex Die Castings! New brackets are cast alumnium alloy and much stronger. If this bracket cracks the roller can actually bend back taking alot of the comntact pressure off the film and scanning drum.

Mark

Posted by Jack Ondracek (Member # 1466) on 02-04-2007, 04:02 PM:

quote: Dave Macaulay
Since there's a slack loop between the projector and soundhead, the projector won't directly produce any flutter in the sound.

But the projector is connected to the soundhead by its geartrain. Binding in the intermittent, for example, could travel back to the soundhead mechanics and that WOULD show up as flutter.

I've also seen situations where the main drive gear on a "C", which is sometimes missed when greasing the machine, can cause rough operation.

Not that any of this is obviously the problem, but since it worked before, it makes sense that it would be an alignment or assembly issue.

Posted by Gordon McLeod (Member # 33) on 02-04-2007, 05:18 PM:

Since the SH1000 should have about 3 perf of slack film in the loop the projector and the gear box should be much of a non issue
I would suspect the roller or the assembly or the bearings of the scanner or the flywheel before anything else

Posted by Bob Koch (Member # 1062) on 02-04-2007, 06:57 PM:

Very seldom is the stabilizer at fault in this reproducer or others of RCA manufacture using a rotary stabilizer. Bearings, yes, and with SH1000 the lateral guide pressure roller is suspect,bad bearings,deformed roller or cracked pot metal casting on upper portion of lateral guide/pressure roller assembly. also defective spring and ball between the upper and lower castings which supplies snubbing pressure to the felt roller against the drum.

Posted by Louis Bornwasser (Member # 3063) on 02-04-2007, 07:11 PM:

I once found 38 of 50 pot metal upper lay on roller holders cracked. 50% fresh break and 50% old break with paint inside the crack from-the-factory. Estimate that these were from 1945 to 1954. Louis

Posted by Gordon McLeod (Member # 33) on 02-04-2007, 07:36 PM:

I have found lots of stabalizer flywheels damaged due to being dropped when moved

Posted by Monte L Fullmer (Member # 2797) on 02-04-2007, 10:23 PM:

Wonder, being an older SH-1000, would this have the fluid filled flywheel instead of the newer solid flywheel?

And something's not working too well with the fluid inside the flywheel causing slight variable rotation speed with the impedence drum shaft?

Posted by Tim Reed (Member # 137) on 02-04-2007, 10:32 PM:

Scott, if it's flutter (as opposed to wowing) I'd certainly check first for flat spots on the sound drum roller felt (or rubber, as the case may be), like Louis, et.al. said.

Also look for cords/cable dragging against the flywheel itself.

Bad bearings, too, as others have mentioned.

Posted by Dave Macaulay (Member # 813) on 02-05-2007, 08:48 AM:

Gordon - one of the ones I rebuilt for Tom had the worm gear bearing loading spring missing and had a pretty nasty flutter. I figured it was from the shaft moving axially and speeding/slowing the sprocket gears while running. I could feel pulsing in the film between the gear and sound drum. After getting new bearings, the missing spring, and fresh oil... it was steady. I can't say for sure that the gearbox was at fault, the pressure roller assembly and drum bearings etc. were all redone at the same time.

Posted by Scott Norwood (Member # 30) on 07-24-2007, 11:56 PM:

Update: this appears to have been fixed.

On the advice of a technician who looked at this, I replaced the bearings, spring, and roller in the "dirt embedder" assembly in the soundhead (Brad's favorite piece of cinema equipment). This seems to have solved the problem. The lower feed sprocket in the projector head and the first sprocket in the soundhead were also swapped with modern VKF sprockets (the old ones were the small CinemaScope sprockets). I'm not sure which of these was (or were) the cause(s) of the issue, but the end result is that everything is fine now. Thanks for all the advice and suggestions above.

Posted by System Notices (Member # 2357) on 02-22-2017, 07:59 PM:

It has been 3500 days since the last post.

Posted by Victor Liorentas (Member # 5272) on 02-22-2017, 07:59 PM:

It's about time to revive this thread! [Smile]

So on my SH1000 SOUNDHEAD...I took off the gear where the take up reel belt goes. So I could slip a new belt on. When I was putting back together I accidentally knocked the key-way off the shaft but didn't realize it at first. When I ran the motor up to speed it rumbled and vibrated loudly. I shut it down and then fixed that. Tried again but it was doing the same shit. Not nearly as bad but still crap. I then tried it with that gear off and it still is bad. The shaft from the motor going to the gear-box is a bit wobbly. It has been that way for a long time but now it's worse. I have another sound-head in the basement. How hard is it to swap out the gear-box?
The coupler is where I see it wobbling...from the gear-box I think. It's a bit stiff when turning by hand compared to the other booth projector.
It vibrates bad as it winds down to a stop.

I only ran it a couple seconds without the key-way on that shaft which gears the projector head and belt to take up reel but it seemed to mess up the motor to gear-box shaft quite a bit. 😞
The good news is the belt seems to work fine. [Roll Eyes]

Posted by Mark Gulbrandsen (Member # 72) on 02-23-2017, 08:07 AM:

Check the motor coupling very carefully, the older they get the more fragile they become. A grumbling gear box is usually that coupling has partially let go, or a failing top bronze gear. IF the gear is shot also be sure to replace the worm gear. If you don't replace it too then the worm will tear the heck out of the new bronze gear in a short time.

Mark

Posted by Victor Liorentas (Member # 5272) on 02-23-2017, 09:57 AM:

Yeah I think it's an issue with the coupling. It wobbles...it always did but I think I made it worse.

Posted by Sam D. Chavez (Member # 1841) on 02-23-2017, 10:12 AM:

Does or did the upper sprocket get hot when the sounded is run? Sure sign of gear trouble. Usually caused by lack of oil but other reasons too.

Posted by Mark Gulbrandsen (Member # 72) on 02-23-2017, 11:30 AM:

Also, a word of advice. In these gear boxes use Mobil 1 synthetic gear lube, 90 weight. If you do the gears will never ever fail. The stuff is also thick enough that it doesn't seep or run out of the gear box.

Mark

Posted by Victor Liorentas (Member # 5272) on 02-23-2017, 11:46 AM:

I never noticed anything got hot...but I caused this issue in a couple of seconds when I ran it without the key way on the belt drive gear which connects to the projector head.

Just now I have made the observation that the spacing between the shaft coming out of the gear box to the coupler is very different on my other projector. The coupler is a good half inch further away from the gear box on the bad projector.
And yes I can move the shaft with my fingers...like it's barely attached to the coupler.

Posted by Victor Liorentas (Member # 5272) on 02-23-2017, 02:26 PM:

Okay so I loosened up the coupler and moved it towards the gear box...tightened it back up and it runs quiet and smooth.
Then I re-engaged the projector head and I dare say it's better than before I started.
Low noise and vibrations. These vibrations may have caused some of my image/focus issues in the past.

The bad news is the v belts I installed for the take up reel. I think they are to stiff and just a bit big. They came off our HVAC.
I'm having no luck finding belts that will work. [Frown]

Posted by Stephan Shelley (Member # 8587) on 02-23-2017, 02:47 PM:

You want the 3L series belts. take a tape measure and measure the circumference of the belt needed. so then it is 3LXX where XX is the inches of the circumference. 25 inches is 3L25

If the 3L is too skinny the go to 4L. 3L is a 3/8 inch wide and 4L is 1/2.

Posted by Steve Guttag (Member # 268) on 02-23-2017, 03:24 PM:

SH1000 should be a 3L belt.

I have in my notes somewhere that a 3L500 and 3L510 have been used with the 510 having an additional note about using it with a Kelmar take up arm.

Note, the pulleys in the later Simplex soundheads are different and need longer belts (same notes mention 3L550 for an SH-1012 to Kelmar arm).

Posted by Victor Liorentas (Member # 5272) on 02-23-2017, 05:02 PM:

Thanks everyone! [Smile]